In the manufacture of electronic devices such as semiconductor devices, a substrate processing apparatus is used. In a chamber of the substrate processing apparatus, gas for processing a substrate is supplied from a gas supply system. The gas supply system includes a flow rate controller which adjusts the flow rate of the gas.
The flow rate of gas is controlled by a flow rate controller such as a pressure control type flow rate controller (FCS) or a mass flow rate controller, but an error may occur between a set flow rate and the flow rate (output flow rate) of the gas which is actually output from the flow rate controller in some cases. Therefore, it is necessary to inspect the output flow rate of the flow rate controller. As a method of inspecting the output flow rate of the flow rate controller, a so-called build-up method is known. The build-up method is described in Japanese Patent No. 5286430.
In the build-up method, gas is output from the flow rate controller at a constant output flow rate, and is supplied to the internal space of a tank having a known volume. Then, while the gas is supplied to the tank, a measured value of the pressure in the internal space is acquired by a pressure sensor. Then, a rise rate of the pressure in the internal space over time is obtained from the acquired measured value, and the output flow rate is obtained by using the rise rate of the pressure. As the tank used in the build-up method, a chamber body of a substrate processing apparatus may be used, or a tank dedicated to the build-up method may be used in some cases.